Lung cancer accounts for more deaths than any other types of cancer in both men and women, with an estimated 226,160 new cases and 160,770 deaths in 2012, in the United States. Although platinum drugs have played a very important role in the chemotherapy of lung cancer, their major limitations are systemic toxicity and the rapid acquisition of resistance. As such, there is an urgent need to develop alternative strategies to effectively treat refractory lung cancer in a clinically-meaningful way without the associated toxicity burden. RNA interference therapy can be a powerful approach to down-regulate specific genes involved in platinum resistance and, therefore, can work synergistically with cytotoxic chemotherapy in refractory lung cancer patients. The main objective of this R21 proposal is to evaluate the therapeutic potential for combination lung cancer therapy using lipophilic (lipid-tailed) platinate derivatives and small interfering RNAs (siRNAs) delivered in CD44- and epidermal growth factor receptor (EGFR)-targeted biocompatible hyaluronic acid (HA) based self-assembling nano-systems. As part of the preliminary studies, we have developed a series of modified HA derivatives, using click chemical conjugation that allow for combinatorial- designed formulation development approach for encapsulation of hydrophobic (e.g., lipid-tailed platinates) and hydrophilic/charged (e.g., siRNA) molecules. Additionally, the modular nano-platform allows for incorporation of additional functionalities, including EGFR specific peptide, for dual targeting in lung cancer. The specific aims of the proposal are as follows: (1) synthesis and characterization of lipid tailed platinate derivatives and encapsulation, along with siRNA duplexes, in HA-based self-assembling nano- systems, (2) evaluation of in vitro gene silencing and cell-kill efficacy using single (lipid-tailed platinate alone) and combination (siRNA+platinate therapy in sensitive A549 and cisplatin-resistant A549DDP human non-small cell lung cancer cells, and (3) establish A549 and A549DDP tumor xenografts in athymic (nu/nu) mice and in vivo evaluation of anti-tumor efficacy and safety of single and combination siRNA/platinate therapy using dual targeting HA-based self-assembled nano-systems. This study is highly significant in evaluating gene silencing strategy in vivo for overcoming tumor drug resistance using a safe and effective delivery system. Following successful completion, future studies in the R01 phase will focus on evaluation of multiple gene silencing and combination therapy delivered with dual targeted HA nanoparticles in a transgenic human lung cancer model.